This invention relates to a vehicle headlamp with a discharge bulb, and more particularly to a sub light distribution pattern forming headlamp.
A discharge bulb is able to perform high brightness irradiation. Hence, recently, it has been employed as the light source of a vehicle headlamp.
In the case where, in such a headlamp with a discharge bulb, a sub light distribution pattern having oblique and horizontal cut lines is formed, the sub light distribution pattern is high in the recognition of far objects, and large in the angle of irradiation.
A headlamp has been proposed in the art which uses a reflector having a reflecting surface including a plurality of reflecting surface elements to reflect the output light of a discharge lamp, thereby to form the aforementioned sub light distribution pattern.
In the case where, as was described above, the reflecting surface of the reflector is made up of a plurality of reflecting surface elements, generally not only a border line which divides the reflecting surface elements into right and left parts but also a border line which divide the reflecting surface elements into upper and lower parts is formed on the reflecting surface.
However, in the case where the border line which divides the reflecting surface elements into upper and lower parts (hereinafter referred to as "an upper and lower border line", when applicable) is carelessly formed on the reflecting surface of the reflector, the following problems are involved:
That is, in the case where, as shown in FIG. 8, the upper and lower border line L is present on the reflecting surface 22 of the reflector 16, the reflecting surface 22 is discontinuous at the upper and lower border line L, and therefore the undercoating paint applied to the reflecting surface 22 for aluminum vacuum deposit treatment forms a paint pool B near the upper and lower boarder line L. This paint pool B is formed not only in the case where, as shown in FIG. 8(a), the upper and lower border line L is of a downward step, but also in the case where, as shown in FIG. 8(b), the upper and lower boarder line L is of an upward step, and in the case where, as shown in FIG. 8(c), the border line L is of a protrusion. And the output light of the discharge bulb 18 applied to the aforementioned paint pool B is reflected in a direction which is different from the aimed direction, to form an upward diffused light Ru, thus glaring on the driver on an oncoming car.
In the case of a conventional headlamp whose light source is a halogen bulb or the like, the upward diffused light from the upper and lower border line causes no serious problem in practical use; however, in the case of a head lamp whose light source is a discharge bulb, the upward diffused light cannot be disregarded because the power of the light source is considerably great.